Interpretive Summary: Bahiagrass is a warm-season grass native to South America which is common in the southeastern United States. One type of bahiagrass, called "Pensacola," has high tolerance to heat and also contains large amounts of wax on the leaf surface. Heat tolerance and leaf surface wax are believed to help plants tolerate the effects of drought. A study was conducted to compare the heat tolerance and leaf wax levels of Pensacola with other types of bahiagrass collected in South America. These two characteristics were studied over two years in a collection of 23 bahiagrass accessions. None of the accessions had a greater level of heat tolerance than did Pensacola. Also, Pensacola was relatively high in leaf wax content, as 16 of the accessions had less leaf wax. Although this study identified accessions that were higher in leaf wax or in heat tolerance, no other accession was superior to Pensacola when both characteristics were considered. This study has identified other bahiagrass accessions with high leaf wax and heat tolerance, and this information will be useful for plant breeders trying to improve the drought tolerance of the species.

Technical Abstract:
Bahiagrass (Paspalum notatum Flugge) is a polymorphic species indigenous to South America which has become naturalized in the southeastern U.S. The most common form in the United States is Pensacola bahiagrass, P. notatum var. saurae Parodi., which is a valuable forage. Pensacola is a sexual diploid, while most other bahiagrasses are apomictic tetraploids. Pensacola bahiagrass is considered to have greater heat tolerance (based on an in vitro heat tolerance test) than a number of other Paspalum species, but has less leaf epicuticular wax (a drought avoidance mechanism) than other species. Both heat tolerance and high leaf epicuticular wax are desirable characteristics for species grown where periodic drought occurs. We measured both characteristics over two years in a collection of 23 bahiagrass accessions, many of which had been collected in South America near the center of origin of the species. The collection included various ploidy levels. For both years, no accessions ranked statistically lower in damage in the heat tolerance test than Pensacola, although eight had significantly higher damage. Two entries in addition to Pensacola had very low damage in the heat tolerance test. Pensacola was high in leaf wax, with 16 accessions rated significantly lower in wax. The accession having the lowest wax content was a triploid, which also exhibited considerable leaf death in the field in response to drought and heat. The diploid entries tended to be higher in leaf wax than the other ploidy levels. This study has identified additional bahiagrass germplasm which may be of use in a breeding program.